Interannual Variability in Carbon Export to the Deep Arctic Ocean

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). The effects of anthropogenically-driven climate change are predicted to be most rapidly and most acutely felt in the Arctic. Two major manifestations of this change are a reduction in sea-ice cover and the destabilization of permafrost soils, both of which will likely alter the arctic carbon cycle. In particular, marked changes in terrestrial carbon fluxes to the ocean and in marine productivity seem inevitable but the overall response of the carbon system in the face of rapidly changing hydrographic and biogeochemical conditions remain unknown. Answers to these questions are crucial to our understanding of whether the Arctic will serve as a net CO2 source or sink to the atmosphere, as well as how coastal and pelagic ecosystems will be perturbed in response to climate change. This project will conduct a detailed examination of flux, sources, mode of delivery, and fate of carbon exported to the deep Arctic Ocean during two consecutive years that coincided with record sea-ice minima (2007-2009). The core sample suite for this investigation stems from time-series sediment traps deployed on a physical oceanographic mooring array in the Canada Basin. By comparing observed fluxes and geochemical characteristics of particulate organic carbon and related biogenic components during this time interval with observations from a prior, more ice-replete period (2004- 2005), and by comparing fluxes for locations currently under seasonal versus perennial ice cover, this research seeks to determine how biogeochemical fluxes to the deep Arctic Ocean vary in response to sea-ice and hydrographic conditions and identify the sources of POC, and the mechanisms of supply to the deep Arctic Ocean. To do this, multiple geochemical tracer approaches will be combined with biogeochemical flux data and synchronous hydrographic measurements to delineate mechanisms that govern carbon export to the deep basin and establish the provenance of this carbon. This will enabale us to gauge future shifts in this system and predict how the arctic carbon cycle may be modified in the face of the climate changes which have been set in motion.

本项目资助依据2009年《美国复苏与再投资法案》（Public Law 111-5）执行。据预测，人为驱动的气候变化对北极地区的影响将最为迅速且显著。该变化的两大主要表现为海冰覆盖范围缩减与永久冻土土壤失稳，二者均可能改变北极碳循环。具体而言，陆地碳向海洋的通量以及海洋生产力的显著变化似乎不可避免，但面对快速变化的水文与生物地球化学条件，碳系统的整体响应仍不明朗。厘清这些问题，对于我们理解北极是否会成为大气二氧化碳的净源或净汇，以及沿海与远洋生态系统将如何响应气候变化发生扰动，均至关重要。本项目将针对2007-2009年这两个海冰覆盖率创纪录最低的连续年份，对输入北极深海的碳的通量、来源、输运模式与归宿展开详细研究。本研究的核心样品组来自部署于加拿大海盆物理海洋学锚泊阵列上的时间序列沉积物捕获器。本研究将该时段观测到的颗粒有机碳（Particulate Organic Carbon, POC）及相关生源组分的通量与地球化学特征，与此前海冰覆盖更完整的时段（2004-2005年）的观测结果进行对比；同时对比当前处于季节性海冰覆盖与常年海冰覆盖区域的通量差异，以此明确输入北极深海的生物地球化学通量如何响应海冰与水文条件发生变化，并确定POC的来源以及其向北极深海输运的机制。为此，本研究将结合多种地球化学示踪方法、生物地球化学通量数据与同步水文测量数据，阐明控制碳向深海盆输运的机制，并明确该碳的来源。这将有助于我们评估该系统未来的变化，并预测在已启动的气候变化背景下，北极碳循环可能发生的改变。